6 Nr. 2. L. KOLDERUP ROSENVINGE: 
particular for Ahnfeltia plicata which has been so often 
examined and is of such common occurrence and so easily 
propagated though it has no vegetative means of propagation. 
For the elucidation of this question I have examined 1) the 
development of the nemathecia and 2) the germination of 
the spores. 
3. Development of the nemathecia. 
At the coasts of Denmark the nemathecia arise in Sep- 
tember. They are not of parasitical origin but appear as 
Fig. 2. First origin of nemathecia. September. 670 : 1. 
small low cushions arising from a group of superficial cells 
growing out simultaneously and dividing by cross walls 
(fig. 2). In September I found the cushions very low, 
only 1—2 cells high. In the middle of October they reach 
a considerably larger size (fig. 3). The extension may be 
up to '/s of the circumference of the frond, and this extension 
is accomplished by the continued production of new nema- 
thecial filaments at the margin. The cells of the nemathecial 
filaments are longer than those of the cortical layer, usually 
2 to 3 times as long as broad and thinner, often only 2 
to 3 w thick; the limit between the cortex and the nema- 
thecium is, however, not always distinct. At the border of 
the nemathecium the filaments are shorter and bent some- 
what outwards. The cells all contain one nucleus; the end- 
